This invention relates to a safety check unit for use in a liquid distribution system, having a pump for distribution of the liquid, to protect equipment of the system from damage associated with loss of pumping capability.
In a liquid distribution system, such as a municipal water or sewage system, a pump is typically provided at least at one end of the distribution system so as to provide the pressure required for distributing the liquid throughout the system. An example of a system of concern is a municipal water system wherein water from a reservoir, for example, is pumped through a series of water mains for eventual distribution to homes, commercial establishments, industrial facilities, and the like. In such a system, it is prudent to protect the pump and associated equipment from damage which could occur if the pump, for whatever reason, suddenly loses head pressure and stops pumping. When such an event occurs, damage can be caused to the pump, distribution manifolds, piping and other equipment associated with the pump.
A number of conditions caused by the sudden loss of pumping pressure must be addressed within seconds of the pressure loss in order to prevent damage to the mentioned equipment. The conditions include: 1) the presence of a negative pressure (in relation to atmospheric pressure) within manifolds, pipelines, fittings, valve bodies, etc. near the pump which potentially can cause cracking or structural failure of those components; 2) a back-flowing of the liquid in the system, with an impact which potentially can cause severe structural damage to the pump, manifolds, pipeline, fittings, valve bodies etc. in the vicinity of the pump; and 3) if such conditions are not addressed properly, pockets of air which can form and which can cause problems upon start-up of the system following the loss of pumping pressure.
Prior art means to overcome the conditions which threaten the pump and related equipment have been cumbersome and complex, they involve many man hours for installation and they require a large amount of space in pumping station facilities. Use of a number of components, each to address a different condition described above, and installed in different locations, increases the possibility of component failure and leakage at joints connecting the piping and the components. Mismatching of size or capacity of the components does not provide the optimum protection. Extensive engineering analysis to match all of the components to each other and to the overall system is required. High labor cost and often compromised assembly of the components, under field conditions, can result in future occurrences of leaks and the like. Positioning of the various components at locations in the system, which may not be the critical location for operating in an optimum manner when loss of pressure or surge occurs, compromises the system.
The various devices, which previously have been provided for controlling the above-mentioned threats to the system include: 1) a check valve, which ideally is piped into the system immediately down stream of the system pump; 2) a surge relief valve, usually positioned at an end of a manifold of the system, but remote from the pump, for receiving and relieving the above-described back-flow surge resulting from the loss of pumping pressure, and 3) an air/vacuum valve, also usually provided at an end of a manifold, or other various locations in the system at a location remote from the pump, to allow air into the system when negative pressure within the system is detected, so as to prevent a vacuum condition, and to allow that air out of the system prior to or during normal operating conditions.
In the present disclosure of the apparatus of the invention, terms such as upstream, downstream, and the like, are used in relation to the flow of the liquid being pumped in a direction to supply the liquid under pressure from the liquid source, through the liquid distribution system to the residential, commercial, and industrial users.
It is an object of the present invention to provide a compact device which incorporates all of the functions necessary to protect a pump, and associated components of a liquid distribution system, from structural damage caused by a sudden drop in the pumping pressure of the pump.
It is another object of the present invention to dispose components of the device, and sensing means required for operation of each component, at an optimum location in the distribution system, and to have components configured for optimum effectiveness in overcoming detrimental conditions.
It is yet another object of the invention to provide a device having all of the features properly sized in relation to each other and integrated for optimum performance, and to provide a device which can be incorporated into a liquid distribution system at solely one critical point of insertion into the system.
It is still another object of the invention to provide a device requiring no electrical, hydraulic or other external support, and requiring no intervention of operating personnel for damage controlling operation of the device or for returning the device back to normal operating conditions following return of the pumping pressure.
The present invention is a safety check unit for use in a liquid distribution system which has a pump and a piping network downstream of the pump for distributing the pumped liquid, wherein the pump intakes a liquid at an intake pressure and outputs the liquid to the piping network at an output pressure which is greater than the intake pressure; and upon terminating pumping, the liquid in the pipe network exerts a back-pressure at the pump which is greater than the intake pressure. The unit is configured for placement in communication with the liquid distribution system downstream of the pump and includes: a liquid checking portion, for checking liquid when back-flowing from the piping network toward the pump, the liquid checking portion having an inlet port in communication with the pump, an outlet port in communication with the distribution system, an internal chamber intermediate the ports and a closing member disposed in the internal chamber for preventing back-flowing of the liquid; a surge relief portion, communicating directly with the internal chamber, for relieving liquid from the system and reducing liquid pressure in the system rapidly when the liquid pressure in the internal chamber is above a pre-selected pressure which is greater than an operating output pressure of the pump; an air input portion, communicating directly with the internal chamber, for providing air to the system when the internal chamber is at least partially void of liquid and a pressure in the void is below atmospheric pressure; and an air release portion, communicating directly with the internal chamber, for releasing air from the system at an adjustable speed when air is in the internal chamber at a pressure above atmospheric pressure.